minaya:
@GoForSmoke, each star contributes to the 'total' flux on the sky with the same amount of photons no matter how the sky is polluted.
There must be something you say that I don't understand.
Parts of the sky, especially at low alt, do get a lot of particles/dust from natural and man-made sources. At night here we have electric generation stations do their stack cleaning (evidenced by the crap laid down for miles with lead, cadmium and mercury as well as sulfur compounds). For well over 10 years now the pall running from India clear across China has cut sunlight by 15% and more, reducing crop yields. Even CLOUDS reflect light back to space... water and dust pollution!
Somehow I don't think that all the photons from Sirius make it to Earth surface. Flying over Earth it's possible to see how much dust and humidity in the lower atmosphere blur details compared to up in the mountains from the same AGL. And up in the mountains where the air is thinner and doesn't have such a load of junk (first time I really understood was on Pike's Peak) objects miles away look very clear where at sea level they're blurred in less than 2 miles.
When a big volcano pops (Krakatoa around 1880) the whole planet cools just from the dust.
Does starlight get through all that with the same photon count? Sunlight doesn't and the Sun is a star.
I've had the chance to see the night sky from 6500 ft (the saddle between Mauna Loa and Mauna Kea) and 8000-9000 (central north New Mexico) up away from any cities before and wow, the sky doesn't just look more clear but far brighter.